Fig. 1. Outline illustration of the review of SCHEHs.

Fig. 2. Photovoltaic effect-based energy harvester. (a) Schematic illustration of the photovoltaic effect-based energy harvester⁴⁴. (b) Simplified scheme presenting the Cl-containing alloy-mediated sequential vacuum deposition approach⁶⁵. (c) Schematic architecture of the flexible OSCs (left), J-V curves of a typical single-junction device (D1:A1) based on FlexAgNEs and ITO glass electrodes (middle), J-V curves of a typical tandem device (D2:A2/D1:A1:A4) based on FlexAgNEs and ITO electrodes (right)⁶⁶. (d) Scheme of the solution ligand exchange process⁶⁷. (e) Schematic diagram of perovskite/SHJ tandem solar cell⁶⁹. (f) Maximum power point tracking of encapsulated tandem solar cells in air. Inset is the photograph of the encapsulated device⁶⁹. (g) Schematic overview of the MAPHEUS-8 sounding rocket flight. Inset is the different illumination states⁷⁰. (h) Scatter plot showing the J_sc evolution and flight-altitude (black line) during micro-gravity⁷⁰. Figure reproduced with permission from: (a) ref.⁴⁴, Copyright © 2019 John Wiley and Sons; (b) ref.⁶⁵, Copyright © 2022 AAAS; (c) ref.⁶⁶, Copyright © 2019 Springer Nature; (d) ref.⁶⁷, under a Creative Commons Attribution 4.0 International License; (e, f) ref.⁶⁹, Copyright © 2023 John Wiley and Sons. (g, h) ref.⁷⁰, Copyright © 2020 Elsevier.

Fig. 3. Triboelectric effect-based energy harvester. (a) Schematic illustration of the triboelectric effect-based nanogenerator⁴⁴. (b) Variation of current and power of the TENG-flag with external load resistances and the output performances of the TENG-flag (the woven unit is 1.5 × 1.5 cm², and the degree of tightness is 1.09) at a 22 m s^-1 wind speed⁷⁸. (c) Voltage profiles of the button battery charged by TENG-flag and galvanostatically discharged at 1 μA⁷⁸. (d) Schematic diagram of the spherical TENG with spring-assisted multilayered structure floating on water, and schematic representation enlarged structure for the zigzag multilayered TENG with five basic units⁷⁹. (e) Schematic diagram of the folded elastic strip-based TENG⁸⁰. (f) Schematic diagram (left) and photographs (middle) of the wearable all-fiber TENG, as well as hundreds of LEDs powered by the TENG⁸¹. Figure reproduced with permission from: (a) ref.⁴⁴, Copyright © 2019 John Wiley and Sons; (b, c) ref.⁷⁸, Copyright © 2016 American Chemical Society; (d) ref. ⁷⁹, Copyright © 2018 John Wiley and Sons; (e) ref.⁸⁰, Copyright © 2015 American Chemical Society; (f) ref. ⁸¹, Copyright © 2015 Elsevier.

Fig. 4. Piezoelectric effect-based energy harvester. (a) Schematic illustration of the piezoelectric effect-based nanogenerator⁴⁴. (b) Schematic structure (left), output voltage (middle), and output current (right) of the lateral-nanowire-array integrated nanogenerator⁸⁵. (c) Schematic diagram of the fabrication process (left) and the photograph (right) of a high-efficient, flexible, and large-area PZT thin film-based NG using the LLO method⁸⁶. (d) Schematic images (left and middle) and the corresponding output voltage (right) of the flexible nanogenerator under the finger movement⁸⁷. (e) Fabrication process (left), SEM image (top), and output current (bottom) of the piezoelectric PVDF nanogenerator⁸⁸. (f) SEM image and the schematic structure of the PZT-PDMS energy harvester⁸⁹. Figure reproduced with permission from: (a) ref.⁴⁴, Copyright © 2019 John Wiley and Sons; (b) ref.⁸⁵, Copyright © 2010 Springer Nature; (c) ref. ⁸⁶, Copyright © 2014 John Wiley and Sons. (d) ref.⁸⁷, Copyright © 2015 Elsevier. (e) ref. ⁸⁸, Copyright © 2010 American Chemical Society. (f) ref. ⁸⁹, Copyright © 2018 American Chemical Society.

Fig. 5. Thermoelectric effect-based energy harvester. (a) Schematic illustration of the thermoelectric effect-based generator⁴⁴. (b) Practical TE generators connecting large numbers of junctions in series to increase operating voltage and spread heat flow²³. (c) Honda prototype TEG exhaust heat recovery system⁹⁷. (d) Schematic illustration (left) and photographs (right) of the complete TEG device on pipe⁹⁸. (e) Structure of the proposed lateral Y type FTEGs¹⁰¹. (f) Practical applications of the fabricated dual-functional sensor as electronic skins¹⁰³. (g) Sketch of the sample preparation of a solution-processable all-polymer TEG¹¹⁰. (h) Performances (left), as well as photographs of the undoped (top) and 40 wt% doped (bottom) thin-film TEGs¹¹⁰. Figure reproduced with permission from: (a) ref.⁴⁴, Copyright © 2019 John Wiley and Sons; (b) ref. ²³, Copyright © 2008 AAAS; (c) ref. ⁹⁷, Copyright © 2016 Elsevier; (d) ref. ⁹⁸, Copyright © 2017 Elsevier; (e) ref. ¹⁰¹, Copyright © 2018 Elsevier. (f) ref. ¹⁰³, under a Creative Commons Attribution 4.0 International License. (g, h) ref.¹¹⁰, Copyright © 2020 John Wiley and Sons.

Fig. 6. SCHEHs based on solar cell and triboelectric nanogenerator. (a) Schematic illustration and the photograph of the hybrid energy harvester¹¹². (b) Architecture of the hybrid TENG/Si tandem solar cell¹¹³. (c) Schematic illustration of the flexible hybrid energy harvesting system¹¹⁴. (d) Scheme of the configuration of the TENG fabrics and the fiber-shaped dye-sensitized solar cell (top), as well as output current of the hybrid energy-harvesting device¹¹⁵. (e) Schematic illustration (left) and the working principle (right) of the raindrop-solar hybrid energy harvester with embedded charge-storage layer¹¹⁶. (f) Photographs and the schematic illustration of the synergistic solar and raindrop hybrid energy harvester¹¹⁷. (g) Schematic diagram of the multifunctional hybrid device¹¹⁸. (h) Schematic illustration of the self-powered environmental visualized system (left), and alterable colored LED showing different light at different environment (right)¹¹⁸. Figure reproduced with permission from: (a) ref.¹¹², Copyright © 2018 American Chemical Society; (b) ref. ¹¹³, Copyright © 2021 Elsevier; (c) ref. ¹¹⁴, Copyright © 2020 Elsevier. (d) ref. ¹¹⁵, Copyright © 2016 John Wiley and Sons. (e) ref. ¹¹⁶, Copyright © 2022 Elsevier; (f) ref. ¹¹⁷, Copyright © 2022 Elsevier; (g, h) ref. ¹¹⁸, Copyright © 2021 Elsevier.

Fig. 7. SCHEHs based on solar cell and piezoelectric nanogenerator. (a) Schematic structure of a serially integrated hybrid cell¹¹⁹. (b) Schematic illustration of a compact hybrid cell¹²⁰. (c) Schematic illustration (left) and the photograph (right) of the tree shaped hybrid nanogenerator¹²¹. (d) Output voltage of the hybrid cell when the pressure is applied periodically at an interval of 3.0 s for an extended period of 1.0 s¹²². (e) Schematic illustration of a composite photovoltaic/PENG film¹²³. (f) Output performance (left) and schematic illustration (middle and right) of the hybrid device with the bending instrument¹²⁴. (g) Experimental configuration of the parallel hybrid power system¹²⁵. Figure reproduced with permission from: (a) ref.¹¹⁹, Copyright © 2009 American Chemical Society; (b) ref. ¹²⁰, Copyright © 2011 John Wiley and Sons; (c) ref. ¹²¹, under a Creative Commons Attribution 4.0 International License; (d) ref.¹²², Copyright © 2015 Elsevier; (e) ref.¹²³, Copyright © 2020 Springer Nature; (f) ref.¹²⁴, Copyright © 2022 Springer Nature; (g) ref.¹²⁵, Copyright © 2021 Springer Nature.

Fig. 8. SCHEHs based on solar cell and thermoelectric generator. (a) Schematic of the PV-TE hybrid power system¹²⁸. (b) Hybrid system efficiency vs. cutoff wavelength for different concentration ratio (h = 10000 W/m² K^-1)¹²⁷. (c) Comparison of the efficiency between the PV-only system and the PV-TE hybrid system¹²⁷. (d) Schematic illustration of the hybrid generation system¹²⁹. (e) Schematic illustration (left), and electron energy band diagram of the PSC-TE hybrid device¹³⁰. (f) Schematic cross section of ZnO nanowires/CIGS solar cell connected to the thermoelectric generator¹³¹. (g) Schematic illustration of the photovoltaic-thermoelectric hybrid device (left), and best performed J-V curves (symbol-line) and output power (dash-line) of the PSC/TE hybrid devices tested with the assisted cooling system or not (right)¹³². ref.¹³², Copyright © 2017 Elsevier. ( h) Non-contact reflection geometry (left), non-contact transmission geometry (middle), and contact transmission geometry (right)¹³⁴. (i) Calculated TEG efficiencies for the PV-TEG hybrid system in the three different geometries¹³⁴. Figure reproduced with permission from: (a) ref.¹²⁸, Copyright © 2014 Elsevier; (b, c) ref. ¹²⁷, Copyright © 2012 Elsevier; (d) ref. ¹²⁹, Copyright © 2013 Elsevier; (e) ref. ¹³⁰, Copyright © 2018 John Wiley and Sons; (f) ref. ¹³¹, Copyright © 2015 John Wiley and Sons; (g–i) ref. ¹³⁴, Copyright © 2021 Royal Society of Chemistry.

Table 1. Comparison of the different types of SCHEHs.